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Biomedical subjects

P Padmos

Publications and source records attributed to P Padmos.

15 recordsLinked to original sources
PubMed1978

Blue cone function in a family with an inherited tritan defect, tested with electroretinography and psychophysics.

The sensitivity of the blue cone system to low frequency flicker was tested with a psychophysical and an electroretinographical method. With the psychophysical method the subjects, members of a family with an inherited tritan defect, showed no sign of the presence of the blue cone system. With the electroretinogram the sensitivity was also significantly lower than in normal subjects, thus indicating a retinal origin of the tritan defect.

Adolescent↗
PubMed1977

Influence of anesthetics, ethyl alcohol, and Freon on dark adaptation of monkey cone ERG.

Cone dark adaptation curves were measured in a rhesus monkey using the electroretinogram (ERG) response to a 40 Hz flickering stimulus. The influence of anesthetics on the time course of dark adaptation was studied. All volatile anesthetics tested (methoxyflurane, halothane, enflurane, ether, chloroform) retarded dark adaptation but to different degrees; urethane, ethyl alcohol, and Freon 11 also retarded dark adaptation. No effect was found for barbiturates and ketamine. It seems unlikely that metabolites play a role in the observed phenomena. A literature survey reveals that several studies on dark adaptation or visual pigment regeneration might have suffered from influences of the anesthetic used. The cause of the phenomenon might lie either in anesthetics-induced membrane changes or in hindrance of the isomeration of 11-trans retinal to 11-cis retinal.

Anesthetics↗
PubMed1975

Cone dark adaptation: the influence of halothane anesthesia.

Cone dark adaptation (da) (measured with an electroretinogram [ERG] method) is found to be severely retarded when the subject (human and macaque monkey) is under halothane anesthesia. The degree of retardation depends both on the halothane level and on the bleach history. The effect of bleach history shows a great similarity with psychophysical findings concerning foveal da. Interpretation of halothane effects, therefore, is possible in terms of an existing model on cone pigment kinetics.

Anesthesia, Inhalation↗
PubMed1974

Identification of cone mechanisms in graded responses of foveal striate cortex.

1. The earliest electrical response detectable in foveal striate cortex of anaesthetized Rhesus monkeys following light stimulation is a graded potential which is positive at the cortical surface and negative in the grey matter and has a peak latency of about 60 msec. The response is similar at both the on- and the off-phase of a light stimulus.2. The relationship of this graded potential to the depth of the recording electrode, to the latency of extracellular impulses and to post-synaptic potentials suggests that it is generated by the depolarization of cortical cells.3. Action spectra obtained in the presence of strong selective chromatic adaptation indicate the participation of all three cone mechanisms in this response.4. Each cone mechanism contributes a similar potential to the response but antagonism between cone mechanisms is apparent. The proportion in which a cone mechanism contributes to the response varies from one area to another implying topographical differences in the representation of cone mechanisms in striate cortex.

Adaptation, Ocular↗